Why: the pre-commit/push mimosa hooks write .mimosa/hook-state inside
the work tree; untracked it marks the Dev superproject dirty
(precheck SHARED_WORKSPACE_BUSY) and blocks card-close gates.
Evidence: git status showed ?? .mimosa after commits; with the ignore
the superproject returns clean. No tracked files affected.
Impact: none at runtime; cache stays local.
Refs: task feature/deliverable-docx-r1 follow-up